A method for measuring the resolution of radiographic testing of a tube-to-tubesheet weld and a test piece

Abstract

The present invention provides a method for measuring the resolution of radiographic inspection of a tube - tube sheet weld and a test piece. The test piece for measuring the resolution provided by the present invention is small in size, low in processing cost, strong in versatility, and convenient to use. By using the test piece according to the method provided by the present invention, the system resolution of radiographic inspection of the tube - tube sheet weld and the image resolution at different positions can be measured. Through simple mathematical transformation, the unsharpness and resolution at different positions of the radiographic inspection of the tube - tube sheet weld can also be calculated.

Description

Technical Field

[0001] The present invention relates to the field of non-destructive testing, and particularly to a test piece for measuring the resolution of radiographic testing of a tube-to-tube sheet weld and a method for measuring the resolution of radiographic testing using the test piece. Background Art

[0002] In fields such as heat exchange devices, steam generators, and heaters, tube-to-tube sheet welded structures are often involved, and they are key processes in the manufacturing process. The number of such welded joints is large, the welding positions are demanding, and the pipe orifice joints are long-term subjected to high temperature, high pressure, and other loads on the tubes, repeated heating, repeated cooling, and the action of medium corrosion fatigue strength damage. Therefore, strict requirements are imposed on the weld tightness and mechanical properties. Therefore, it is extremely important to assess the welding quality of the pipe orifice. The welding quality of the tube-to-tube sheet weld largely affects the service life of the heat exchange device. Especially in the nuclear power field, the application conditions of the steam generator are more demanding, and higher requirements are imposed on the welding of the tube-to-tube sheet. It is necessary to conduct a comprehensive inspection of the weld to ensure that the steam generator can operate normally under high temperature and high pressure.

[0003] To verify the welding quality of the tube-to-tube sheet weld, currently, penetration testing and radiographic testing are mostly used. Based on current production practice experience, a sensitivity identification test is used to ensure that the sensitivity of radiographic testing meets the testing requirements. During the sensitivity identification test, different specifications of small holes are mostly machined on the weld surface of the welded specimen of the tube-to-tube sheet weld to represent different sensitivity levels. This method has high costs, low efficiency, and poor versatility. It can only verify the detection sensitivity of volumetric defects such as pores on the workpiece surface and cannot measure the system resolution of radiographic testing of the tube-to-tube sheet weld, the image resolution at different positions, the unsharpness, and the resolving power.

[0004] Therefore, there is an urgent need for a method for measuring the resolution of radiographic testing to ensure that the performance such as the system resolution of radiographic testing of the tube-to-tube sheet weld of shell-and-tube heat exchange devices such as steam generators, the image resolution at different positions, the unsharpness, and the resolving power meet the testing requirements. Summary of the Invention

[0005] To solve the above problems, the inventors of the present invention have conducted intensive research and provided a resolution test piece for measuring the resolution of radiographic testing of a tube-to-tube sheet weld. The resolution test piece is convenient to use and has strong versatility. It can measure the system resolution of the radiographic testing system and the image resolution, unsharpness, and resolving power at multiple different detection positions, thus completing the present invention.

[0006] The purpose of the first aspect of the present invention is to provide a resolution test piece for measuring the resolution of radiographic testing of a tube-to-tube sheet weld, and the resolution test piece is provided with a plurality of slot pairs.

[0007] The object of the second aspect of the present invention is to provide a method for measuring the resolution of a tube-to-tube sheet weld by ray detection. The method uses a resolution test piece for measurement and specifically includes the following steps:

[0008] Step 1: Select a resolution test piece according to the tube end diameter of the ray detection tooling;

[0009] Step 2: Perform radiography on the resolution test piece;

[0010] Step 3: Analyze the detection results and calculate the resolution.

[0011] The beneficial effects of the present invention include:

[0012] (1) The resolution test piece in the present invention is small in size, strong in versatility, low in processing cost, convenient to use, flexible in disassembly and assembly, and can also adjust the position, so that the resolution of multiple different detection positions can be measured.

[0013] (2) The method for measuring the resolution of a tube-to-tube sheet weld by ray detection provided by the present invention is easy to operate and implement, and is convenient for quickly determining the ray detection resolution.

[0014] (3) The method for measuring the resolution of a tube-to-tube sheet weld by ray detection provided by the present invention can not only measure the system resolution, but also measure the image resolution, unsharpness and resolution of multiple different positions. Description of the Drawings

[0015] Figure 1 Shows a schematic diagram of a resolution test piece in an embodiment of the present invention;

[0016] Figure 2 Shows a detailed schematic diagram of a pair of slots on the resolution test piece in an embodiment of the present invention;

[0017] Figure 3 Shows a schematic diagram of the detection tooling in an embodiment of the present invention;

[0018] Figure 4 Shows a schematic diagram of measuring the resolution of a ray detection system in an embodiment of the present invention;

[0019] Figure 5 Shows a schematic diagram of measuring the image resolution at different positions of ray detection in an embodiment of the present invention.

[0020] Explanation of the Reference Numerals in the Drawings

[0021] 1 - Resolution test piece;

[0022] 101 - Pair of slots;

[0023] 102 - Central hole;

[0024] 103 - Center hole center of the test piece;

[0025] 104 - Groove to the end circumference;

[0026] 105 - Radial fan-shaped groove;

[0027] 106 - Central angle of the radial fan-shaped groove;

[0028] 107 - Central angle between two radial fan-shaped grooves separated by the groove;

[0029] 2 - Tube end of the ray detection tooling;

[0030] 3 - Imaging element of the ray detection tooling;

[0031] 4 - Interface end of the ray detection tooling;

[0032] 5 - Ray source focus;

[0033] 501 - Ray beam;

[0034] 6 - Gasket;

[0035] 7 - Spacer block. Specific implementation manner

[0036] The present invention will be described in detail below through specific implementation manners, and the features and advantages of the present invention will become clearer and more definite along with these descriptions.

[0037] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "upper", "lower", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or part referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0038] The present invention provides a resolution test piece 1 for measuring the ray detection resolution of a tube-tube sheet weld.

[0039] The resolution test piece 1 is a thin sheet with parallel upper and lower surfaces, and its outer contour can be a polygon or a circle, and a central hole 102 perpendicular to the surface is provided at its center. There are multiple groove pairs 101 on the resolution test piece 1. A typical implementation manner of the resolution test piece 1 is as Figure 1 shown.

[0040] The upper and lower surfaces of the resolution test piece 1 should be parallel and flat. Preferably, the flatness and parallelism tolerances of the upper and lower surfaces of the resolution test piece 1 should not exceed ±0.05 mm.

[0041] The outer contour of the resolution test piece 1 is polygonal or circular, which can be arbitrarily set according to needs, but it shall not affect the function of the slot pair 101. Through research, it is found that the distance from the contour boundary to the circumference of the end of the slot pair 104 shall not be less than 5 mm to meet the requirements.

[0042] For the central hole 102 of the resolution test piece 1, the cylindrical surface thereof shall be perpendicular to the upper and lower surfaces of the resolution test piece 1, its shape shall be the same as that of the pipe end 2 of the ray detection tooling, its diameter shall be matched with the pipe end 2 of the ray detection tooling, preferably larger than the diameter of the pipe end 2 of the ray detection tooling, and the difference shall not exceed 1 mm.

[0043] There are multiple slot pairs 101 on the resolution test piece 1. The details of the slot pair 101 are as Figure 2 shown. Each slot pair 101 is composed of two radially fan-shaped ring grooves 105 with the same geometric dimensions. The top view of the radially fan-shaped ring groove 105 is fan-shaped or its horizontal section is fan-shaped, the center of the circle it faces is the center hole center 103 of the test piece, its top arc is on the circumference of the central hole 102, its bottom arc is on the circumference of the end of the slot pair concentric with the central hole 102 of the test piece, and its two side edges are along the radial direction of the central hole 102 of the resolution test piece 1. There is a gap between the two radially fan-shaped ring grooves 105 in each slot pair 101, and the central angle 107 of the gap between the two radially fan-shaped ring grooves in the slot pair 101 is equal to the central angle 106 of the two radially fan-shaped ring grooves in the slot pair 101. The radially fan-shaped ring groove 105 is a through groove penetrating the upper and lower surfaces of the resolution test piece 1, and its surface is perpendicular to the upper and lower surfaces of the resolution test piece 1, and it can be made by wire cutting or other suitable processing methods. During use, in order to prevent the deformation of the gap between the two radially fan-shaped ring grooves 105 in the slot pair 101 on the resolution test piece 1, a non-absorbing material with a ray absorption coefficient much lower than that of steel, such as hard plastic or resin, can be filled in the radially fan-shaped ring groove 105.

[0044] On the resolution test piece 1, the top arcs of all the radial fan-shaped annular grooves 105 are on the circumference of the central hole 102 of the test piece, and the bottom arcs are on the same groove pair end circumference 104 concentric with the central hole 102 of the resolution test piece 1. The central angles 106 of the radial fan-shaped annular grooves of different groove pairs 101 are different. The value of the central angle 106 of the radial fan-shaped annular groove ranges from 0.1° to 10°, and the angular tolerance is preferably not more than ±10% of the selected value. Preferably, the central angle is in the range of 0.5° to 5°. When there are multiple values of the central angle 106 of the radial fan-shaped annular grooves on the resolution test piece 1, the values of a geometric progression with a common ratio are preferably selected. Further preferably, the common ratio is less than the ratio of the diameter of the groove pair end circumference 104 to the diameter of the central hole 102 of the resolution test piece 1. The groove pairs 101 with the same central angle 106 of the radial fan-shaped annular grooves are regarded as groove pairs 101 of the same specification. The groove pairs 101 of the same specification are centrally symmetrically distributed on the resolution test piece 1 with the center of the circle of the central hole of the test piece 103 as the center of symmetry. There are at least two groove pairs 101 of one specification on one resolution test piece 1. When there are two or more specifications of groove pairs 101 on the resolution test piece 1, the distance between different specification groove pairs 101 should be large enough to avoid interference between the images of the groove pairs 101 on the imaging element; the different specification groove pairs 101 are arranged in a clockwise or counterclockwise order according to the size order of the central angles 106 of their radial fan-shaped annular grooves, so as to facilitate the image recognition of the groove pairs 101 on the imaging element.

[0045] The diameter of the groove pair end circumference 104 and the maximum value of the central angle 106 of the radial fan-shaped annular groove on the resolution test piece 1 jointly determine the lower limit value of the resolution measurement range of the resolution test piece 1. The diameter of the top arc of the radial fan-shaped annular groove 105 and the minimum value of the central angle 106 of the radial fan-shaped annular groove on the resolution test piece 1 jointly determine the upper limit value of the resolution measurement range of the resolution test piece 1. The diameter of the groove pair end circumference 104 and the maximum and minimum values of the central angle 106 of the radial fan-shaped annular groove should be reasonably arranged to meet the usage requirements. Through a large number of experimental studies, a typical implementation scheme that can be widely applied is that the diameter of the groove pair end circumference 104 is 2.5 times the diameter of the central hole 102 of the resolution test piece 1. There are 3 specifications of groove pairs 101 on the resolution test piece 1, a total of 6, and the central angles 106 of the radial fan-shaped annular grooves in different specification groove pairs 101 are 1°, 2° and 4° respectively.

[0046] In the present invention, the thickness of the resolution test piece 1 is related to the ray absorption coefficient of the material used. The greater the ray absorption coefficient of the material, the smaller the thickness can be. When the material of the resolution test piece 1 is lead, tungsten or other materials with comparable ray absorption coefficients, its thickness can be 0.1 mm. When the material of the resolution test piece 1 is Inconel alloy, brass or other materials with comparable ray absorption coefficients, its thickness can be 1 mm. When the thickness of the resolution test piece 1 is small, or the hardness and stiffness of the material used are small, in order to prevent the resolution test piece 1 from deforming during use, the resolution test piece 1 can be encapsulated in a non-absorbing material such as rigid plastic or resin with a ray absorption coefficient much smaller than that of steel. Regardless of the material used, the thickness of the resolution test piece 1 does not exceed 2 mm.

[0047] The method for measuring the ray detection resolution of the tube-to-tube sheet weld provided in the present invention uses the resolution test piece 1 for measurement and calculation, and specifically includes the following steps:

[0048] Step 1: Select the resolution test piece 1 according to the diameter of the tube end 2 of the ray detection tooling.

[0049] A typical ray detection tooling for tube-to-tube sheet welds is as Figure 3As shown in the figure. Generally speaking, this detection tooling consists of three parts, including the tube end 2 of the ray detection tooling, the imaging element 3 of the ray detection tooling, and the interface end 4 of the ray detection tooling. When performing ray detection on the tube - tube sheet weld, usually insert the tube end 2 of the ray detection tooling into the tube of the tube - tube sheet weld. When performing fluoroscopy, the ray source focus 5 emits a ray beam 501 in the tube end 2 of the ray detection tooling. Among them, the effective ray beam 501 is the part that can penetrate the detection area and form an image on the imaging element 3 of the ray detection tooling. According to different ray detection techniques used, the imaging element 3 of the ray detection tooling can be generally divided into three categories: the ray film system, the digital imaging system, and the phosphor imaging system. When using the ray film photography technique (RT technique), the imaging element 3 of the ray detection tooling is usually the ray film system, including a filter plate, an intensifying screen, a ray film, a shielding plate, etc. After fluoroscopy, it needs to be processed in a darkroom to form a ray negative film, and then observed and measured on a viewing lamp. When using the ray digital imaging technique (DR technique), the imaging element 3 of the ray detection tooling is usually a digital imaging device (digital detector), and after fluoroscopy, it can be directly observed and measured on a display after computer processing. When using the ray computer - aided imaging technique (CR technique), the imaging element 3 of the ray detection tooling is usually a phosphor imaging plate (IP plate), and after fluoroscopy, it can be directly observed and measured on a display after being scanned by a dedicated laser scanner and then computer processing. According to different types of rays used, the interface end 4 of the ray detection tooling can be connected to a power source or a source conduit. When using X - rays, an X - ray machine is installed at the interface end 4 of the ray detection tooling. When performing fluoroscopy, the power supply needs to be turned on so that X - rays can be generated at the ray source focus 5 in the tube end 2 of the ray detection tooling. When using γ - rays, the interface end 4 of the ray detection tooling is connected to the source conduit to form a passage, and when performing fluoroscopy, the γ - ray source is transported to the ray source focus 5 in the tube end 2 of the ray detection tooling through the source conduit.

[0050] In the present invention, the shape of the central hole 102 of the resolution test piece 1 should be the same as that of the tube end 2 of the ray detection tooling, the diameter of the central hole 102 should be matched with the tube end 2 of the ray detection tooling, preferably slightly larger than the diameter of the tube end 2 of the ray detection tooling, and the difference does not exceed 1 mm. Determine the diameter of the central hole 102 of the resolution test piece 1 according to the diameter of the tube end 2 of the ray detection tooling for which the resolution is to be measured. Ensure that the resolution test piece 1 can be smoothly sleeved on the tube end 2 of the ray detection tooling, and the gap is less than 1 mm.

[0051] Step 2: Perform fluoroscopy on the resolution test piece 1.

[0052] When it is necessary to measure the resolution of the tube - tube sheet weld ray detection system, directly sleeve the resolution test piece 1 on the tube end 2 of the ray detection tooling, as Figure 4 shown. Adjust the ray fluoroscopy process parameters so that a clear ray image of the resolution test piece 1 can be obtained on the imaging element 3 of the ray detection tooling.

[0053] When it is necessary to measure the resolution at different positions of the radiographic inspection of the tube-to-tube sheet weld, the distance between the resolution test piece 1 and the imaging element 3 of the radiographic inspection tooling is adjusted by adding a gasket 6 under the resolution test piece 1, as Figure 5 shown. In order to eliminate the resolution difference caused by different ray penetration thicknesses, a spacer 7 is also required to be added to the resolution test piece 1. The gasket 6 is a thin sheet with parallel and flat upper and lower surfaces and a central through hole. Its material can be carbon steel, low alloy steel or stainless steel. Its outer contour is not less than that of the resolution test piece 1. The central through hole is perpendicular to the upper and lower surfaces, and the shape and diameter of the central through hole are preferably the same as those of the resolution test piece 1. For convenient use, the thickness of the gasket 6 can be 0.5 mm or 1 mm, so as to adjust the distance between the resolution test piece 1 and the imaging element 3 of the radiographic inspection tooling by stacking layers. The spacer 7 has parallel and flat upper and lower surfaces, and a central through hole perpendicular to the surface. The shape and diameter of the through hole are preferably the same as those of the resolution test piece 1. The outer shape of the spacer 7 only needs to ensure that it can cover the range of all effective ray beams 501 emitted from the ray source focus 5 that can penetrate the resolution test piece 1 and be imaged on the imaging element 3. Adjust the radiographic exposure process parameters so that a clear ray image of the resolution test piece 1 can be obtained on the imaging element 3 of the radiographic inspection tooling.

[0054] Step 3: Analyze the test results and calculate the resolution.

[0055] Observe the radiographic exposure image of the resolution test piece 1 obtained from the imaging element 3 of the radiographic inspection tooling. Observe the point of the smallest groove pair 101 where the images of two radial fan-shaped annular grooves 105 can just be clearly distinguished. This point is the maximum resolution point. The arc length corresponding to the interval between the two radial fan-shaped annular grooves 105 in the groove pair 101 on the resolution test piece 1 at this point is the resolution value, in units of mm. Twice the resolution value is the unsharpness value, in units of mm. The reciprocal of the unsharpness value is the resolution value, in units of lp / mm (line pairs per millimeter).

[0056] Next, use simple trigonometric relations to find the arc length corresponding to the interval between the two radial fan-shaped annular grooves 105 in the groove pair 101 on the resolution test piece 1 at the maximum resolution point.

[0057] Since the groove pairs 101 of the same specification are centrally symmetrically distributed on the resolution test piece 1 with the center of the central hole 103 of the test piece as the center of symmetry, the maximum resolution point should also be centrally symmetrically distributed with the center of the central hole 103 of the test piece as the center of symmetry. Measure the distance L between the two points (in units of mm).

[0058] According to the production scheme of the resolution test piece 1 and the recognizable situation of the images of the groove pairs 101 on the test piece, it is easy to know that the central angle 106 of the radial fan-shaped annular groove of the groove pair 101 where the maximum resolution point is located is θ (in units of degrees).

[0059] According to the ray detection tooling used, the distance F (unit: mm) between the focus 5 of the ray source and the imaging unit in the imaging element 3 of the ray detection tooling can be known. When using the radiographic film technique (RT technique), the imaging unit is the radiographic film; when using the digital ray imaging technique (DR technique), the imaging unit is the digital imaging plate (digital detector); when using the computed radiography technique (CR technique), the imaging unit is the IP plate.

[0060] According to the placement position of the resolution test piece 1, the distance H (unit: mm) between the resolution test piece 1 and the imaging unit in the imaging element 3 of the ray detection tooling can be known. Usually, the imaging element is inside the imaging element 3 of the ray detection tooling. Even when using the Figure 4 fluoroscopic method shown, H is greater than 0.

[0061] Substituting the above values into the following formula, the resolution d (unit: mm) can be calculated.

[0062]

[0063] Among them, π is the pi.

[0064] The unsharpness value is twice that of d, and the unit is mm.

[0065] The resolution value is the reciprocal of the unsharpness value, and the unit is lp / mm, that is, line pairs per millimeter.

[0066] When using the Figure 4 fluoroscopic arrangement shown, the measured resolution is the resolution of the ray detection system, and this resolution has nothing to do with the part to be inspected.

[0067] When using the Figure 5 fluoroscopic arrangement shown, the measured resolution is the image resolution at different positions of the ray detection.

[0068] Example

[0069] Measure the system resolution and the image resolution at 2 mm of the γ-ray detection of a certain tube-to-tube sheet weld.

[0070] For the ray detection of the tube-to-tube sheet weld of the steam generator of a pressurized water reactor nuclear power plant, the γ-ray radiographic film technique is used for detection with an Ir192 ray source.

[0071] (1) Select the resolution test piece 1 according to the diameter of the tube end 2 of the ray detection tooling.

[0072] In this embodiment, the diameter of the tube end 2 of the ray detection tooling is 15.5 mm. The selected resolution test piece 1 is made of Inconel alloy (material grade N06690). The outer contour of the resolution test piece 1 is a circular wafer with a diameter of 50 mm. The central hole 102 of the resolution test piece 1 is a circle with a diameter of 16 mm. The thickness of the resolution test piece 1 is 1 mm. There are 6 groove pairs 101 on the resolution test piece 1, and there are 3 types of their specifications. The corresponding central angles 106 of the radial fan-shaped grooves are 1°, 2° and 4° respectively. The groove pairs 101 are arranged counterclockwise in ascending order of the central angle 106 of their radial fan-shaped grooves. The diameter of the circumference 104 at the end of the groove pair is 40 mm. The central angle formed by the center lines of any two adjacent groove pairs 101 is 60°. Any groove pairs 101 of the same specification are symmetrically distributed in the center of the test piece, and the central angle formed by their center lines is 180°.

[0073] (2) Radiograph the resolution test piece.

[0074] Adopt as Figure 4 shown radiographic arrangement, directly put the resolution test piece 1 on the tube end 2 of the ray detection tooling, and measure the resolution of the tube-tube sheet weld ray detection system. At this time, the distance H1 between the resolution test piece 1 and the imaging unit in the imaging element 3 of the ray detection tooling is 3 mm.

[0075] Adopt as Figure 5 shown radiographic arrangement, put two gaskets 6 under the resolution test piece 1 and put a spacer 7 on the resolution test piece 1 to measure the image resolution at 2 mm of the tube-tube sheet weld ray detection. At this time, the distance H2 between the resolution test piece 1 and the imaging unit in the imaging element 3 of the ray detection tooling is 5 mm.

[0076] The gasket 6 is a circular thin sheet with a diameter of 60 mm and a thickness of 1.0 mm. There is a through hole perpendicular to the upper and lower surfaces in the center. The diameter of the through hole is 16 mm, and the material is austenitic stainless steel (material grade 304). The spacer 7 is a circular ring with a diameter of 45 mm and a thickness of 15 mm. There is a through hole perpendicular to the upper and lower surfaces in the center. The diameter of the through hole is 16 mm, and the material is austenitic stainless steel (material grade 304).

[0077] The imaging unit in the imaging element 3 of the ray detection tooling is Carestream M100 film (film system category is C2 level according to GB / T 19348.1).

[0078] The interface end 4 of the ray detection tooling is connected to the source conduit to form a passage. During radiography, the Ir192 γ-ray source with a focal size of Φ0.5 mm is transported to the ray source focus 5 in the tube end 2 of the ray detection tooling through the source conduit. The distance F between the ray source focus 5 and the imaging unit in the imaging element 3 of the ray detection tooling is 30 mm. The activity of the ray source is 0.51 Ci.

[0079] Adjust the exposure time to obtain a clear radiographic image of the resolution test piece 1 on the radiographic film. When measuring the resolution of the tube - tube sheet weld radiographic testing system using the Figure 4 shown radiographic arrangement, the exposure time is 60 s. When measuring the image resolution at 2 mm of the tube - tube sheet weld radiographic testing using the Figure 5 shown radiographic arrangement, the exposure time is 150 s.

[0080] (3) Analyze the test results and calculate the resolution.

[0081] Develop the exposed radiographic film in the darkroom using an automatic film processor and Carestream machine - developing kit. The developing time is 3 minutes, the developing temperature is 28 °C, the fixing time is 5 minutes, and the fixing temperature is 28 °C. The blackness of the developed film is between 2.2 and 3.7, meeting the evaluation requirements.

[0082] Observe the resolution test radiographic film and find the maximum resolution point, that is, the point of the smallest groove pair 101 where the two radial fan - shaped annular grooves 105 can just be clearly distinguished. Measure the distance L (unit: mm) between the two points.

[0083] Upon observation, on the radiographic film of the system resolution test, the central angle 106 of the radial fan - shaped annular groove of the groove pair 101 where the maximum resolution point is located is 1°, that is, θ is 1°. The measured distance L1 is 37.5 mm. Substitute it into formula (1) for calculation, and the obtained resolving power d1 is 0.294 mm, the unsharpness is 0.588 mm, and the system resolution is 1.70 lp / mm.

[0084] Upon observation, on the radiographic film of the 2 - mm image resolution test, the central angle 106 of the radial fan - shaped annular groove of the groove pair 101 where the maximum resolution point is located is 2°, that is, θ is 2°. The measured distance L2 is 31.0 mm. Substitute it into formula (1) for calculation, and the obtained resolving power d2 is 0.451 mm, the unsharpness is 0.902 mm, and the image resolution is 1.11 lp / mm.

[0085] The present invention has been described in detail above in combination with specific embodiments and / or exemplary examples and the drawings. However, these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications, or improvements can be made to the technical solutions and their implementation manners of the present invention, and all of these fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A resolution test piece for radiographic testing of a tube-to-tube sheet weld, characterized in that a plurality of slot pairs (101) are provided on the resolution test piece (1), and the slot pairs (101) are composed of two radially fan-shaped annular slots (105) with the same geometric dimensions; the resolution test piece (1) is provided with a central hole (102), the central hole (102) is perpendicular to the upper and lower surfaces of the resolution test piece (1), and its shape is the same as that of the tube end (2) of the radiographic testing tooling; there is a gap between the two radially fan-shaped annular slots (105) in the slot pair (101), and the central angle (107) of the gap between the two radially fan-shaped annular slots in the slot pair (101) is equal to the central angle (106) of the two radially fan-shaped annular slots in the slot pair (101).

2. The resolution test piece for radiographic testing of the tube-tubesheet weld according to claim 1, characterized in that, The diameter of the central hole (102) is larger than the diameter of the tube end (2) of the radiographic testing tooling, and the difference does not exceed 1 mm; The outer contour of the resolution test piece (1) is polygonal or circular.

3. The resolution test piece for radiographic testing of a tube-to-tube sheet weld according to claim 1, characterized in that when the material of the resolution test piece (1) is lead or tungsten, its thickness is 0.1 mm, and when the material of the resolution test piece (1) is Inconel alloy or brass, its thickness is 1 mm; In order to prevent the resolution test piece (1) from deforming during use, the resolution test piece (1) is encapsulated in a rigid plastic or resin material; The thickness of the resolution test piece (1) does not exceed 2 mm.

4. The resolution test piece for radiographic testing of a tube-to-tube sheet weld according to claim 1, characterized in that the horizontal cross-section of the radially fan-shaped annular slot (105) is fan-shaped, the center of the circle it faces is the center of the central hole of the test piece (103), its top arc is on the circumference of the central hole (102), its bottom arc is on the circumference (104) at the end of the same slot pair concentric with the central hole (102) of the test piece, and its two side edges are along the radius of the central hole (102) of the resolution test piece (1); the radially fan-shaped annular slot (105) is a through slot penetrating the upper and lower surfaces of the resolution test piece (1), and its surface is perpendicular to the upper and lower surfaces of the resolution test piece (1).

5. The resolution test piece for radiographic testing of a tube-to-tube sheet weld according to claim 4, characterized in that the central angles (106) of the radially fan-shaped annular slots of different slot pairs (101) on the resolution test piece (1) are different; the value of the central angle (106) of the radially fan-shaped annular slot is 0.1° to 10°.

6. The resolution test piece for radiographic testing of a tube-to-tube sheet weld according to claim 5, characterized in that the value of the central angle (106) of the radially fan-shaped annular slot is 0.5° to 5°.

7. The resolution test piece for radiographic testing of a tube-to-tube sheet weld according to claim 5, characterized in that when there are multiple values of the central angle (106) of the radially fan-shaped annular slots on the resolution test piece (1), the values are those of a geometric progression with a common ratio, and the common ratio is less than the ratio of the diameter of the circumference (104) at the end of the slot pair to the diameter of the central hole (102) of the resolution test piece (1).

8. The resolution test piece for radiographic testing of a tube-to-tube sheet weld according to claim 1, characterized in that Groove pairs (101) with the same central angle (106) of the radial fan-shaped annular grooves are groove pairs (101) of the same specification; Groove pairs (101) of the same specification are centrosymmetrically distributed on the resolution test piece (1) with the center of the central hole of the test piece (103) as the center of symmetry; There are at least two groove pairs (101) of one specification on one resolution test piece (1); When there are two or more specifications of groove pairs (101) on the resolution test piece (1), the different specification groove pairs (101) are arranged clockwise or counterclockwise according to the size order of the central angles (106) of their radial fan-shaped annular grooves.

9. The resolution test piece for radiographic inspection of the tube-tubesheet weld according to claim 4, characterized in that The diameter of the circumferences (104) at the ends of the groove pairs is 2.5 times the diameter of the central hole (102) of the resolution test piece (1); There are three specifications of groove pairs (101) on the resolution test piece (1), and the central angles (106) of the radial fan-shaped annular grooves in the different specification groove pairs (101) are 1°, 2° and 4° respectively.

10. A method for measuring the resolution of radiographic testing of a tube-to-tube sheet weld, characterized in that, The method uses the resolution test piece (1) described in any one of claims 1 to 9 for measurement.

11. The method for measuring the ray detection resolution of a tube-tubesheet weld according to claim 10, characterized in that, The method specifically includes the following steps: Step 1, select the resolution test piece (1) according to the diameter of the tube end (2) of the radiographic inspection tooling; Step 2, perform radiography on the resolution test piece (1); Step 3, analyze the test results and calculate the resolution.

Images